[Rcpp-devel] List of Lists to List of Vectors

[Tim Keitt]

On Mon, May 4, 2015 at 2:37 PM, Dirk Eddelbuettel <edd at debian.org> wrote:

>
> On 4 May 2015 at 14:23, Tim Keitt wrote:
> |
> |
> | On Sun, May 3, 2015 at 11:29 PM, Antonio Piccolboni <
> antonio at piccolboni.info>
> | wrote:
> |
> |     Check here  for something similar to Tim's solution that
> preallocates all
> |     vectors to avoid the costly push_back. Still needs the unlists in R,
> so
> |     it's expensive in that dimension, the number of lists in the output.
> |
> |
> | I may have a way around the unlist part; still needs testing.
>
> Keep us posted.
>
> | push_back is amortized constant so only a little costly.
>
> But going from std::list to SEXP is one full copy.  Not so bad in the grand
> scheme of things.
>

Copying is where all the costs accumulate for sure. I find it mostly
guesswork whether something copies or not with Rcpp data structures.

THK


>
> Dirk
>
> --
> http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org
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